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net: introduce a new tracepoint for tcp_rcv_space_adjust 

tcp_rcv_space_adjust is called every time data is copied to user space,
introducing a tcp tracepoint for which could show us when the packet is
copied to user.

When a tcp packet arrives, tcp_rcv_established() will be called and with
the existed tracepoint tcp_probe we could get the time when this packet
arrives.
Then this packet will be copied to user, and tcp_rcv_space_adjust will
be called and with this new introduced tracepoint we could get the time
when this packet is copied to user.
With these two tracepoints, we could figure out whether the user program
processes this packet immediately or there's latency.

Hence in the printk message, sk_cookie is printed as a key to relate
tcp_rcv_space_adjust with tcp_probe.

Maybe we could export sockfd in this new tracepoint as well, then we
could relate this new tracepoint with epoll/read/recv* tracepoints, and
finally that could show us the whole lifespan of this packet. But we
could also implement that with pid as these functions are executed in
process context.

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Yafang Shao 2018-04-20 23:18:26 +08:00 committed by David S. Miller
parent 48d7a07ba3
commit 6163849d28
2 changed files with 23 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

30
include/trace/events/tcp.h
View File

@ -10,6 +10,7 @@
#include <linux/tracepoint.h>
#include <net/ipv6.h>
#include <net/tcp.h>
#include <linux/sock_diag.h>
#define TP_STORE_V4MAPPED(__entry, saddr, daddr) \
do { \
@ -113,7 +114,7 @@ DEFINE_EVENT(tcp_event_sk_skb, tcp_send_reset,
*/
DECLARE_EVENT_CLASS(tcp_event_sk,
TP_PROTO(const struct sock *sk),
TP_PROTO(struct sock *sk),
TP_ARGS(sk),
@ -125,6 +126,7 @@ DECLARE_EVENT_CLASS(tcp_event_sk,
__array(__u8, daddr, 4)
__array(__u8, saddr_v6, 16)
__array(__u8, daddr_v6, 16)
__field(__u64, sock_cookie)
),
TP_fast_assign(
@ -144,24 +146,34 @@ DECLARE_EVENT_CLASS(tcp_event_sk,
TP_STORE_ADDRS(__entry, inet->inet_saddr, inet->inet_daddr,
sk->sk_v6_rcv_saddr, sk->sk_v6_daddr);
__entry->sock_cookie = sock_gen_cookie(sk);
),
TP_printk("sport=%hu dport=%hu saddr=%pI4 daddr=%pI4 saddrv6=%pI6c daddrv6=%pI6c",
TP_printk("sport=%hu dport=%hu saddr=%pI4 daddr=%pI4 saddrv6=%pI6c daddrv6=%pI6c sock_cookie=%llx",
__entry->sport, __entry->dport,
__entry->saddr, __entry->daddr,
__entry->saddr_v6, __entry->daddr_v6)
__entry->saddr_v6, __entry->daddr_v6,
__entry->sock_cookie)
);
DEFINE_EVENT(tcp_event_sk, tcp_receive_reset,
TP_PROTO(const struct sock *sk),
TP_PROTO(struct sock *sk),
TP_ARGS(sk)
);
DEFINE_EVENT(tcp_event_sk, tcp_destroy_sock,
TP_PROTO(const struct sock *sk),
TP_PROTO(struct sock *sk),
TP_ARGS(sk)
);
DEFINE_EVENT(tcp_event_sk, tcp_rcv_space_adjust,
TP_PROTO(struct sock *sk),
TP_ARGS(sk)
);
@ -232,6 +244,7 @@ TRACE_EVENT(tcp_probe,
__field(__u32, snd_wnd)
__field(__u32, srtt)
__field(__u32, rcv_wnd)
__field(__u64, sock_cookie)
),
TP_fast_assign(
@ -256,15 +269,14 @@ TRACE_EVENT(tcp_probe,
__entry->rcv_wnd = tp->rcv_wnd;
__entry->ssthresh = tcp_current_ssthresh(sk);
__entry->srtt = tp->srtt_us >> 3;
__entry->sock_cookie = sock_gen_cookie(sk);
),
TP_printk("src=%pISpc dest=%pISpc mark=%#x length=%d snd_nxt=%#x "
"snd_una=%#x snd_cwnd=%u ssthresh=%u snd_wnd=%u srtt=%u "
"rcv_wnd=%u",
TP_printk("src=%pISpc dest=%pISpc mark=%#x length=%d snd_nxt=%#x snd_una=%#x snd_cwnd=%u ssthresh=%u snd_wnd=%u srtt=%u rcv_wnd=%u sock_cookie=%llx",
__entry->saddr, __entry->daddr, __entry->mark,
__entry->length, __entry->snd_nxt, __entry->snd_una,
__entry->snd_cwnd, __entry->ssthresh, __entry->snd_wnd,
__entry->srtt, __entry->rcv_wnd)
__entry->srtt, __entry->rcv_wnd, __entry->sock_cookie)
);
#endif /* _TRACE_TCP_H */

2
net/ipv4/tcp_input.c
View File

@ -582,6 +582,8 @@ void tcp_rcv_space_adjust(struct sock *sk)
u32 copied;
int time;
trace_tcp_rcv_space_adjust(sk);
tcp_mstamp_refresh(tp);
time = tcp_stamp_us_delta(tp->tcp_mstamp, tp->rcvq_space.time);
if (time < (tp->rcv_rtt_est.rtt_us >> 3) || tp->rcv_rtt_est.rtt_us == 0)